DE2234573A1 - NUCLEAR STEAM GENERATOR - Google Patents

Description

sDe.

PATENT ADVOCATE

η. July 1972 Application files: 27.27

PATENT APPLICATION

Applicant: BABCOCK & WILCOX COMPANY,

161 East 42nd Street, New York, N.Y. 10017 - USA -

Title: Nuclear Steam Generator

The invention relates to an improved power generation system with a single generating device in the form of a nuclear reactor, which is equipped with a number of steam generators in the form of replaceable and "write-off" modules, in order to achieve an optimum of effective and efficient medium evaporation during the energy generation process.

In engineering there are many and different nuclear 'power generation systems, some of which are dependent on the evaporation of media such as B. Water, hang out. However, in order to maintain serviceability, long service life and to be able to ensure safety, these generation systems must necessarily be supported by a great many individual and separate auxiliary systems, each of which

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has its own space requirements due to its size and shape. Ultimately, there is such an intricate operational fabric of auxiliary systems a somewhat large, cumbersome and proportionate one Ineffective system compared to the size of the construction site required for installation, maintenance and use.

For example, in public-sector companies such as a Kraftwerk ^ the need up to 1200 MW. in the more common single-core force generators which in the past usually required no less than a mere space for maintenance and operation

46400 μ. And if it were necessary, like them Environmentalists demand that such a plant be built in an underground concrete bed, then the same plant had to be built be placed at depths as great as 90 m.

Also, e.g. in other applications, e.g. as a ship propulsion system, the speed of a nuclear-powered ship is, among other things, controlled by the Space available for the power generation system is limited. Limited according to the current state of the art the usual nuclear power generation system for ship propulsion

Output to a maximum of 325 MW, primarily because of the overall

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space requirements on the part of the reactor and auxiliary systems. So is the propulsion of such a ship is limited to around 120,000 shaft horsepower. As it should be clear, it is indeed one of the deterrents For the use of nuclear energy in many cases the storage space required, which is not only due to the reactor itself but also to the necessary auxiliary systems.

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In technology, a system is required that is in the form of a Power generation system is switched, but not essentially all of the auxiliary systems required according to the state of the art needed for their operation, maintenance and use in an effective and efficient manner, but nevertheless offers an optimum in the area of security.

The present invention meets the needs of the art with regard to this the three-dimensional requirements for size and shape with particular emphasis on a nuclear power generation system that Can be used to generate benefits beyond those go beyond the prior art without the following auxiliary systems essentially from the circuit according to the present invention can be taken out:

a) Drives for control rods in partial length;

b) core flooding systems;

c) high pressure injection systems;

d) thiosulphate spray systems;

e) feeding and withdrawal systems for soluble poisons;

f) instrumentation systems within the core;

g) enormously large computer systems;

h) Also large systems for liquid waste disposal;

i) Support systems for earthquake cycles.

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As a side advantage of switching off the above systems, the periodic testing and maintenance of such auxiliary systems are also included
off their space and cost requirements.

It is therefore an object of the invention to provide an improved core system for generating power without the need for the
above auxiliary systems.

Another object is to provide an improved nuclear power generation unit to create that has internally replaceable steam generators of the "write-off" modular design.

Another task is to build a steam generator of the modular design to create in order to achieve an optimum of effective and efficient evaporation of the medium during the energy generation process.

Other objects and many ancillary advantages of this invention will become
will become more apparent to those skilled in the art when he detailed the following
Description reads in conjunction with the accompanying drawings.

An embodiment of the invention is shown in the drawing and is described in more detail below. They show:

1 shows a diagram of the flow system,

Fig. 2 shows a cross section of the reactor with a particular arrangement the internals,

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Fig. 3 is a section along the line 3-3 of Fig. 2, showing a grid consisting of a number of steam generators around the perimeter of the reactor core.

Fig. 4 is a view taken along line 4-4 of Fig. 3 and is shown an overall group consisting of a number of the individual reactor-steam generator modules.

FIG. 5 shows a view of an individual steam generator module of the reactor according to FIG. 2.

FIG. 6 is a view taken along line 6-6 of FIG. 5, and FIG. 7 is a view taken along line 7-7 of FIG. 5.

Like numerals mean like parts within the different ones Illustrations.

One aspect of the invention as shown in FIG. 1 includes in the broad sense of the word a power generation system that is connected in a closed circuit and several nuclear reactor steam includes generating units, which are each connected in parallel to two coupling units, which are part of the closed system circuit form and are arranged in series therein. According to this circuit, any reactor aggregate or any number of such Reactor units are incorporated into the flow sequence to give a performance range of 1 to 3 times the system performance. if z. B. if a genset has an output of 400 MW, then one would have an output of

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1200 MW can be achieved by placing the three units in the closed Circulatory system operates in parallel. It does not, however, imply that this achievement is achieved without the auxiliary systems which are required when using the prior art single nuclear reactor with the same overall performance begins.

In detail, in the system according to the present invention, each of the consolidated core steam generators 11 is connected to a coupling unit or mixing chamber 12 via corresponding fittings, to direct steam to a turbine 13 for conventional power generation. A capacitor 14 is in series with the Turbine 13 switched and is located near a pump 15, which condensate to a desalinator 16 and then in series via a Air jet apparatus 17, a low pressure preheater 18 and one Degassing preheater 19 conducts. A main pump 21 takes over feed water from the preheater 19 and directs it to a high pressure preheater 22 for the purpose of forwarding to the selected core steam generator 11 Via a coupling 23 and corresponding fittings.

Further side advantages of the invention include the fact that a complex of this kind can be accommodated spatially on construction sites which would not be possible to use the nuclear power generation system consisting of a single reactor can absorb comparable performance. The security advantages offered by the present system and the spatial arrangement far exceed those of other systems using light water reactors; same-

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the system or the system can be serviced and operated more easily in good time. Furthermore, there is the generation of liquid waste negligibly small, since a relatively low level of radioactive contamination is built up.

Referring now to Figure 2, the consolidated core steam generator 11 according to the invention is with a pressure vessel 26 equipped, which has a conventional core 27, which consists mainly of a grid of fuel elements, the coolant flow channels set within the core. A heat exchanger or steam generator 28 is in primary coolant flow connection with the container 26 and is equipped with devices 29 to transfer primary coolant through the generator 28 and the container 26 to let such channels flow. The tank is also equipped with devices for supplying feed water 31 and steam 32, each of these devices with the aforementioned closed circuit system according to FIG. 1 is coupled.

The essence of the process and the reactor arrangement is that a single steam generator is provided at a distance above the core in the pressure vessel 28. The primary coolant flow path is indicated by the points 35 to 39 in FIG. As you can see from the picture, each of the steam generator building blocks is Provided below with a support plate 41 and with a support wall 42, which extends in the longitudinal direction along the inside of the block which is described in detail below.

Previous efforts to develop a pressurized water reactor

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of the integral type shown in Fig. 2 are through a typical Incompatibility between the respective shapes and dimensions of the main parts, e.g. core, core container and steam generator, complicated been designed. Even after solving some of the shape problems to create a more compact reactor, it was found that the prior art arrangements increased manufacturing costs and created additional problems associated with the Maintenance and driving in the company were linked * That was why a reactor arrangement as shown in Fig. 2 is aimed at in order to achieve the desired degree of compactness, however while eliminating the additional costs and traffic problems.

A high degree of compact design has been achieved with the arrangement shown in FIG. 2 due to the steam generator 28 and due to its shape and size. As a result, both the height and the diameter of the pressure vessel have been greatly reduced with a corresponding reduction in the primary coolant requirement to as little as 50% of the requirement for conventional individual reactors according to the prior art, while the present arrangement is relatively free of thermal stresses, which caused by operational transitional states.

Other side advantages are that the steam generator is at a distance are arranged above the core. In practice, the distance should have a total dimension of at least about 60 cm. on in this way the generation of radioactive oxygen in the secondary system is avoided; this also separates the secondary problems

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which include the use of expensive shielding within such a system. There is an additional benefit in that activated corrosion products are also avoided in the secondary system. This has occurred in the past usually, one, as metallic tubes with a neutron field came into contact from the reactor core. As a result of the advantages mentioned, ferritic steel can be used in the manufacture of the steam generator can be used, which is relatively cheaper and for optimizing the efficiency of the heat exchange process has greater thermal conductivity than stainless steel. In the past, the use of such a material was not possible · This was primarily due to the fact that when the distance between the steam generator is reduced and the cord has the usual tendency to crack and break of the ferritic ones Steels increases.

Since auxiliary systems were used in the past, boric acid contained in the primary coolant, the ferritic steels could also not be used because of the corrosion rate. However, such a material can now be used, and Due to the greater thermal conductivity of these materials, the steam generators can be manufactured in smaller and cheaper units without endangering the required total heat transfer of such a unit. Further would be the steam flow path raise significant technical, operational and maintenance problems when, as in the past, the steam generator is alongside the core would be arranged. In the arrangement shown in Fig. 2, however, there is a relatively low flow resistance.

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got up in the primary system and a natural cycle is maintained, even if the pump 29 fails. Indeed, the circulation in the present reactor would be opposed in such a case the total natural cycle or the total current even something else that is commonly found in prior art reactors. This means that even when the circulation pumps are not working achieved unusually good behavior in this regard. According to the invention, the heat exchangers or steam generators 28 for use in the reactor takes the form of a multitude of individual and replaceable building blocks, each of which is "written off" can be and all together the heat transfer process of the system and, as described, the flow distribution of the coolant control in such a unit. It is known in the art that the performance of a nuclear reactor is inter alia the coefficient is limited with which heat can be transferred to the secondary medium flowing within the heat exchanger.

A design to ensure the optimum in effective and effective heat transfer between a primary and secondary medium within the aforementioned reactor is the one in which a number of longitudinally extending heat exchange tubes, which a Secondary medium contained within a prescribed space in a certain order in the flow path of the heated one Primary medium is arranged. In such a case, the primary medium flows downwards over a maximum outer surface of the tubes and It transfers its heat to the secondary medium within a each of the tubes; this secondary medium is easily evaporated, producing steam or gas. The latter steam or that

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The latter gas then flows upwards within such tubes in countercurrent to the primary medium. In order for the system to be optimal To ensure heat transfer, the tube bundles are in groups 40 manufactured, which are called building blocks and arranged side by side around the circumference of the core in the overall shape of a grid 41 as can be seen from FIG. 3.

The grid shown in Fig. 3 consists of a number evenly built, lengthways and juxtaposed building blocks of steam generating units.

However, the overall configuration of the grid in the arrangement can be somewhat can be changed without departing from the spirit of this invention as long as each of the steam generators 28 forming the grille 41 is on individual, separable and replaceable building block of the type described in detail below. Furthermore, as shown in Fig. 4, to achieve a perfectly free flow of the primary medium through the grid or the entire steam generator the individual Steam generator groups 42 arranged at different heights to each other, whereby the primary medium is essentially unhindered in the, flows through and out of the steam generator as it does through the flow lines 43 is indicated. As shown, a system of manifolds 44 is provided to remove the steam from the building blocks through the wall of the container 26 to lines 32 of the total energy generation system, as shown in Fig. 1 to conduct. It should be noted that the extended pieces are a each of the individual tubes 47 are arranged side by side in the middle of the building blocks 42, even if each of the steam generators

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units of the group are at a different level. The whole The group of steam generators forms a number of longitudinal flow channels for the primary medium. Although the building blocks lie at different heights, the middle, non-drawn-in part of the individual drawn-in pipe pieces rests on all building blocks the same height. This arrangement maintains the effectiveness of the heat exchange surface upright, because it avoids the tendency that any single pipe is bypassed by the flowing primary medium will. As shown in FIG. 5, the individual building block or the individual steam generating unit 28 is essentially a closed one Package of longitudinal tubes 47, which are precisely arranged and held to one another, with a meaningful freedom between the same exists so that they can expand with the change in temperature. The bundle consisting of longitudinal tubes becomes stable between two Tube sheets 50, 51 held, each of which in communication with another Share the base for the inlet and outlet headers of the closed System forms and which hold the bundle against rattling and vibrations when the unit is heated in eddy currents is exposed to flowing primary medium. In general, the unit is laterally spaced along its length by a Stabilized component, which is called grate 52. The latter part eliminates the risk that the individual pipes through Bend or shift in temperature or turbulence. In some cases the rust could be through a number of Fitted tabs are formed to form a side mesh structure to result in openings in which the longitudinal tubes are received and held in a grid-like manner, without the flow of the primary medium Is obstructed over the individual pipes. As indicated,

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the latter medium flows in the longitudinal direction along and within of the pipe structure as a carrier for the heat or energy transfer on the individual tubes.

As shown in Fig. 5, the individual run relatively thin, vertical tubes through the top and bottom horizontal tube sheets side by side at specific distances from each other. the The outer surface of the tube sheets or side adjacent parts is on the contact points of these tube sheets with the outer ends of each Tubes preferably flat and level. In the manner described, the unit represents a compact package of bundled tubes. The methods of attaching such tubes to tube sheets are numerous and include electric welding or any other common or a conventional method known in the art for this desired purpose.

Another advantage is the improved access to the steam generator 28 in the reactor itself, because the entire installation, the is arranged above the core, can be expanded as a unit. The latter unit consists of the outer walls 42, which give the steam generator an internal support and are braced in the longitudinal direction by stiffening ribs 43, the in turn extend vertically and are supported by the plates 44-47. After the installation described has been removed, a easy access to the individual groups of steam generators possible. In this way each of the building blocks can easily be replaced, ' "written off" or even repaired on the spot. There is also less time compared to the known prior art

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required to fully expand each of the steam generator modules and replace. Leakages in the individual pipes of a building block can also be easily blocked off in a relatively less degradation in performance.

In a preferred embodiment, the bricks would have a square cross-section and a pitch that corresponds with size and division of the core fuel assembly is compatible. Essentially it was found that the once-through steam generator with its low secondary velocities and upward flow is uniquely suitable for the required building block shape. The individual tubes of the building block preferably have a wall thickness of about 1.7 mm and a section with an outer diameter of about 12.7 mm, which at both ends to an outer diameter of is pulled in about 9.5 mm. The division in a practical

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Block is about 15.5 mm. The primary coolant flow into and out of each of the building blocks is facilitated by the retracted pipe section. The typically small drilling diameter of the building blocks reduces the leakage rate in the case of a pipe rupture and contributes to the compact design; In addition, it reduces the need for thick walls on the pipes themselves to a minimum

The individual headers 52, 53 shown in Figures 6 and 7 are either forged or cast. This individual Pieces are welded to the tube sheet as shown in FIG is. Each of the headers is provided with a peripheral edge 54 which is attached to the tube sheet. The inside of the The main body of each of the collectors is against the external pressure

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of the primary medium is supported by a number of evenly distributed nozzles 55, which bear against the tube sheet when the Edge is welded on. Since the internal pressure is considerably less than the external pressure, it is not necessary to have any of these Welding socket on the contact surface of the tube sheet.

The steam generator modules are preferably divided into groups of nine and ten and, as shown above, into at least three vertical layers arranged to each other in order to allow an unrestricted flow of the Pcimärmediums. Also, each building block can be free in the vertical direction in operational transition states expand or contract due to the elasticity in the distribution line. Furthermore, the container feedthroughs are for the Feed water inlets and steam outlets generally symmetrical in each quarter circle of the tank.

During operation, primary water flows downwards in a longitudinal direction the steam generator pipes at about the same speed as it prevails in the core. Feed water or the secondary medium abandoned by entering the feedwater pipe 56. The feed water then flows down to the lower block collector and is evenly distributed to each boiler tube by the lower header; when it flows vertically upwards through the tubes 47, it is evaporated and superheated in order to be distributed in the upper collector, via the opening 60, to the distributors of the power generation unit of the system to be collected.

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Experimental results have shown that the steam generator building block is free of critical or unusual stability problems with or without pulling in the individual boiler tubes.

In the system described above, leaky pipes can be shut off without interrupting the operation of the system. Under pressure, the pipe walls of the generator are less affected by damage and are less prone to stress corrosion cracking. The pipes can and should not work at lower stresses leak even if they collapse. The individual steam generators also do not need the special workshop equipment like a conventional unit. Thus the building block is good for Suitable for mass production processes which previously could not be used in the manufacture of steam generators for pressurized water reactors *

In conclusion, it can be said that the previously described and compared The extreme compactness of the system available for performance results in great savings in manufacturing, maintenance and operation of a power plant. The special construction and arrangement of the reactor itself has erased the belief that pressurized water reactors difficult to maintain and navigate. In addition, such a system requires fewer and uncomplicated auxiliary systems Security systems which tend to add to the cost of an ordinary conventional system.

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Claims (2)

PATENT CLAIMS: SSSSBBSSSSBBSSSrsSSSSSSSSSSSBSBSSSSBSSKaSSSBS: In a nuclear power generation system with provision for at least two separate flow paths in the heat exchange ratio to each other, wherein one of the named paths contains a heated primary medium and a second of the named ones Ways a secondary medium in a convertible state depending on the temperature change, the improvement in the form of a number of building blocks for use in said heat exchange, each full: a) a number of collectors spaced apart the upper of said headers having a closed passage and an exit; b) a feed pipe, which is inserted operationally through the said passage and with it in terms of flow communicating with said lower header; c) a number of hollow longitudinal tubes fluidically connected to said upper and said lower Collectors are in communication and arranged in a pattern with respect to said esophagus; with the secondary medium in the liquid state downwards flows through said feed pipe and in the lower one - 18 - 20 9 8 84 / 10A0 Collector is distributed to up through the longitudinal pipes and from the opening in the upper header in the gaseous State to pour out, wherein said conversion of the state of the secondary medium takes place essentially in the longitudinal tubes, Over which the heated primary medium is in a heat exchange ratio flows. 2. Device according to claim 1, characterized in that that said primary and secondary flow paths of the Media are switched to one another in countercurrent. 3. Device according to claim 2, characterized in that the heat exchange between the primary medium and
the secondary mediura occurs in any of a number of individually switchable parallel partial flow paths which originate from and lead to the main secondary flow path. 4. Device according to claim 2, characterized in that the heat exchange between the primary medium and
the secondary medium takes place completely in a number of individually switchable parallel partial flow paths that originate from the main secondary flow path and lead to the same * 5. Device according to claim 2, characterized in that each of the longitudinal tubes ends in two end pieces,
each of which on a separate tube sheet of each
Collector is attached. - 19 - 2 0 9884/10 4 0 6. Device according to claim 3, characterized in that that the end pieces of each of the longitudinal tubes are drawn in in the area located in the vicinity of the tube sheet and that the middle section of all longitudinal tubes is at the same height as one another. 7. In a nuclear reactor equipped with a pressure vessel which has a core made up of fuel assemblies defining coolant flow paths within the core, wherein a heat exchanger within said container on the primary coolant side Is in fluid communication with the core and there are devices to circulate primary coolant through the To convey exchanger and core via the flow paths mentioned, the improvement in the form of a heat exchanger made up of a number of building blocks, including: a) a number of collectors spaced apart are, the upper one of the headers having a closed passage and an exit; b) a feed pipe that is inserted through the passage for operational purposes and with the lower collector in terms of flow communicates; c) a number of hollow longitudinal tubes which fluidically communicate with the upper and lower headers stand and arranged in a pattern with respect to the feed tube; - 20 - 209884/1040 being a secondary medium in a * depending on the temperature change convertible state in liquid form down through the Feed pipe flows and is distributed in the lower header to up through the longitudinal pipes and out of the opening in to flow out of the upper collector in the gaseous state to an external energy generation circuit, wherein the conversion of the state of the secondary medium takes place essentially in the longitudinal tubes, over which the heated Primary medium flows in a heat exchange ratio. 8. Nuclear reactor according to claim 7, characterized in that that the number of building blocks in the form of a grid spaced above the core along an upward extension of the core circumference is arranged. 9. A heat exchanger module for use in the evaporation of a secondary medium, comprising: a) a number of collectors spaced apart, the upper one of which is closed Has passage and one exit; b) a feed pipe that is inserted through the passage for operational purposes and with the lower collector in terms of flow communicates; c) a number of hollow longitudinal tubes which are fluidically connected to the upper and lower headers and are arranged in a pattern with respect to the feed pipe / - 21 - 209884/1 OAO with the secondary medium in the liquid state downwards flows through the feed pipe and is distributed in the lower header to up through the longitudinal pipes and out to flow out of the opening in the upper collector in the gaseous state, wherein said conversion of the secondary medium im takes place essentially in the longitudinal tubes when a heated primary medium is in the heat exchange ratio over the longitudinal pipes flows. 10. Heat exchanger according to claim 1, characterized in that that the longitudinal tubes are spaced around the feed tube. 2 0 9 8 8 Λ / 1OAQ Blank page